Hi @mark1,
If you think you will go for the Nomad3 or Shapeoko Pro, it would be worthwhile to download, install and learn Carbide Create software (it’s free and you can get it here. You could create your square hole and circular holes, and create toolpaths for them using the default feeds and speeds from the tool library for aluminium: CC will display an estimated cutting time, and you can then experiment to see how it is affected by the various cutting parameters.
Let’s say you took the feeds and speeds recommended in the MaterialMonday series of videos, fourth video from the top, “Aluminium feeds and speeds for the Nomad”, for a 1/8" 2-flute endmill (102-Z)
10.000RPM, 20 inch per minute, 0.012" depth per pass, 0.0625" stepover
=> one cutting pass in your 2"x1" pocket would take (2 x 1 / 0.0625) / 20 = 1.6 minute
=> to get all the way through 1mm will take 4 passes, so that pocket would take about 6.4minutes.
Each hole will probably add a minute or so, so I guess you would be looking at something in the 10-15min ballpark.
The Nomad3 and SO Pro XXL are obviously very different machines so it really depends on the quantity and size of pieces you would like to produce, as well as the tolerances you are after. The Nomad3 should have better precision, but as you noted will not be able to reach the same material removal rate you could get on a SO Pro with 1/4" or larger endmills. If you need e.g. to make lots of parts with moderately tight tolerances, the large work area of the SO Pro could turn out to be very useful to mill tens of them at a time.